APRÈS LE DÉLUGE : ÉVOLUTION GÉOMORPHOLOGIQUE DU DELTA DU DANUBE APRÈS LA RECONNEXION MER NOIRE - MÉDITERRANÉE ET SES IMPLICATIONS SUR LE PEUPLEMENT ÉNÉOLITHIQUE / CHALCOLITHIQUE

International audienceIn this work, we document the evolution of the upper Danube delta (i.e. blocked delta) using archaeological, geomorphological and geoarchaeological approaches, after the discovery, in the 90's, of the oldest human settlement (Eneolithic/Chalcolithic) close to Mila 23 district. In-site and out-site fieldwork allows us to refine the Danube delta early evolution from 5,600 to 4,000 cal. yr BC. During this period, it functions like a fresh bayhead delta, flowing into a huge lagoon isolated from the open sea by the Letea-Caraorman spit. Then, lagoon water level rose rapidly due to an eustatic rise, and possibly from an unusual highstand of sealevel resulting from wet conditions. The settlement was then partially flooded and abandoned around 4,450 cal. yr BC.Dans ce travail, l'évolution de la zone interne du delta du Danube est appréhendée à partir de travaux géoarchéologiques et géomorphologiques réalisés dans le district de Mila 23, suite à la découverte de la plus vieille occupation humaine (énéolithique/ chalcolithique) du delta dans les années 90. Les travaux sur site et hors site ont permis de préciser les stades précoces de l'évolution du delta entre 5 600 et 4 000 ans cal. av. J.-C. Celui-ci évolue comme un delta lagunaire en eau douce, s'épandant dans un large lagon séparé de la mer par la ride de Letea-Caraorman. La remontée rapide du niveau lagunaire, sous l'effet de la remontée eustatique et peut-être d'une sur cote liée à un événement humide, ont conduit à une submersion partielle du site et probablement à son abandon vers 4 450 ans cal. av. J.-C

Aftermath of the flooding : geomorphological evolution of the Danube delta after the black sea-mediterranean reconnection and its implications on eneolithic settlements

International audienceIn this article we document the evolution of the internal area of the Danube Delta (i.e. the blocked delta) starting from the geo-archaeological and geomorphological investigations performed at Mila 23 district, following the discovery of the oldest human settlement in the Delta. The in-site and out-site field work and coring allowed us to specify the delta's early stages of evolution from 5600 to 4000 CAL BC. During this period, the site evolves as a freshwater bay-head delta flowing into a huge lagoon isolated from the open sea by Letea-Caraorman spits. The rapid sedimentation rate in the lagoon is interpreted as a response to base-level rise and overflooding as a result of humid conditions during 6-5 ky RCC, leading to the partial submersion of the site and probably to its abandonment around 4450 CAL BC

Porosity Density and Physical Properties of Deep-Sea Sediments from the Black Sea

During the August 2004 cruise of ship Mare Nigrum, sediment cores with a maximum length of 4 meters were taken with a gravity corer from several sites in the Black Sea, at depths of 860 to 1414 meters. All cores were characterized by the presence of deep-sea sediments typical of the Black Sea, that is coccolith ooze, sapropel, grey and black clay. Measurements of porosity as well as of other physical properties (bulk saturated density, grain density, water content and shear strength) were performed on two cores. Porosity values are situated within normal limits for these types of sediments, ranging from 71 to 80%, with the exception of coccolith ooze and most notably sapropel, characterized by exceptionally high values exceeding 90%. Bulk saturated density and water content values are in proportion with porosity values. Grain density values are highly homogenous, ranging from 2.60 to 2.72 gr/cm³, with the exception of previously mentioned muds with exceptionally low values ranging from 2.41 to 2.51 gr/cm³. Shear strength measurements were performed on soft sediments and resulted into very low values ranging from 9 to 43 gr/cm³, which are too close to the equipment’s accuracy to allow for them to be used beyond the purpose of information

Geo-ecological Assessment of Tuzla Lake (Constanţa County, Romania)

Abstract. Tuzla Lake emerged in the 70’s as an extension of Techirghiol Lake. The forming of the lake occurred due to human factors (intensive irrigations) and was favoured by natural factors (years of intense pluvial regime). The periodical increase of the Tuzla Lake level produced flooding in the area; the most recent ones (September 2005) significantly affected the buildings and the land around Tuzla Town. In order to evaluate the geo-ecological state of Tuzla Lake, including the impact from the last flooding events on the morphology of the lacustrine basin, the following investigations were performed: bathymetry measurements, sedimentological evaluations, and determination of the physico-chemical, chemical and microbiological parameters of the water. These investigations were performed during 2005 and 2006, and they consisted of the periodical sampling of the water and sediments as well as of bathymetry measurements sensu stricto before and after the 2005 flooding events. The central area of Tuzla Lake has a positive morphological element directed N-S, which divides the basin of the lake in two distinct areas: a western area, maximum 2m deep, and an eastern area, over 1.5m deep. Following the September 2005 floods, a decrease in the depth of the lake by 60-70cm in the southern part of the lake and by 30cm in the northern part occurred. Probably, one of the effects of the flood was the partial clogging of the lake. The lithology of the samples analyzed (mud, silt) indicates that the Tuzla Lake sediments are specific to a lacustrine environment. The aquatic environment is eutrophic (high level of nutrients and reduced oxygen level), an environment suggested by the blackish colour and the oily consistency which is specific to the sapropelic muds. The laboratory analysis results indicate low values for dissolved oxygen, and values significantly above the standards for PO4 2, SO4 2-, as well as high salinity values (30-40 ‰). Therefore, it was concluded that the water in Tuzla Lake is polluted. This observation, along with the fact that there was an excess of lake vegetation that favoured an increase in anophelic habitats, indicates the fact that Tuzla Lake presents a hazard for the human health of the communities in the area

Après le Déluge : évolution géomorphologique du delta du Danube après la reconnexion Mer Noire - Méditerranée et ses implications sur le peuplement énéolithique / Chalcolithique

Dans ce travail, l’évolution de la zone interne du delta du Danube est appréhendée à partir de travaux géoarchéologiques et géomorphologiques réalisés dans le district de Mila 23, suite à la découverte de la plus vieille occupation humaine (énéolithique/chalcolithique) du delta dans les années 90. Les travaux sur site et hors site ont permis de préciser les stades précoces de l’évolution du delta entre 5 600 et 4 000 ans cal. av. J.-C. Celui-ci évolue comme un delta lagunaire en eau douce, s’épandant dans un large lagon séparé de la mer par la ride de Letea-Caraorman. La remontée rapide du niveau lagunaire, sous l’effet de la remontée eustatique et peut-être d’une surcote liée à un événement humide, ont conduit à une submersion partielle du site et probablement à son abandon vers 4 450 ans cal. av. J.-C.In this work, we document the evolution of the upper Danube delta (i.e. blocked delta) using archaeological, geomorphological and geoarchaeological approaches, after the discovery, in the 90’s, of the oldest human settlement (Eneolithic/Chalcolithic) close to Mila 23 district. In-site and out-site fieldwork allows us to refine the Danube delta early evolution from 5,600 to 4,000 cal. yr BC. During this period, it functions like a fresh bayhead delta, flowing into a huge lagoon isolated from the open sea by the Letea-Caraorman spit. Then, lagoon water level rose rapidly due to an eustatic rise, and possibly from an unusual highstand of sealevel resulting from wet conditions. The settlement was then partially flooded and abandoned around 4,450 cal. yr BC